Fail-safe device for chemically armed mines

ABSTRACT

A safety device is provided for inclusion into a dispenser for permeable chemically armed mines which are stored in a desensitized state by immersion in certain halocarbon liquids. A fluid which will permanently sterilize or deactivate the explosive composition of the mine is encapsulated in a sealed frangible container. The container is then partially enclosed in a polymeric material which has the property of swelling while under the influence of certain organic liquids and then forcefully contracting when this influence is absent, thereby breaking the container and permitting the encapsulated material to contact and permanently desensitize the explosive. For example, KOH encapsulated in a glass ampoule which is, in turn, enclosed in a tube of buna rubber. This device can be inserted in a dispenser loaded with chemically armed mines containing lead azide and RDX as the explosive, the dispenser is then filled with 1,1,2 trichloro- 1,2,2 trifluoro ethylene, to insure desensitization until activation is desired.

lUted Stes atent 1 [111 3,750,527 Heinemann 1 Aug. 7, 1973 iFAlL-SAFEDEVICE FOR CHEMHCALLY [57] ABSTRAQT ARMED MINES [75] Inventor: Robert W.Heinernann, Dover, NJ.

[73] Assignee: The United States of America as represented by theSecretary 011 the Army, Washington, DC.

[22] Filed: May 11, 1972 [21] Appl. No.: 252,168

{58] Field of Search 86/1; 102/1, 57, 102/8 [56] References Cited UNITEDSTATES PATENTS 3,138,100 6/1964 Peschko 102/8 3,667,387 6/1972 Picard etal 102/57 Primary Examiner-Benjamin R. Padgett Attorney-Harry M.Saragovitz et a].

breaking the container and permitting the encapsulated material tocontact and permanently desensitize the explosive.

For example, KOH encapsulated in a glass ampoule which is, in turn,enclosed in a tube of buna rubber. This device can be inserted in adispenser loaded with chemically armed mines containing lead azide andRDX as the explosive, the dispenser is then filled with 1,1,2 trichloro-1,2,2 trifluoro ethylene, to insure desensitization until activation isdesired.

7 Claims, 3 Drawing Figures PAIENIE m". 7 I973 SHEET 2 [1F 2 FAIL-SAFEDEVICE FOR CHEMICALLY ARMED MINES The invention described herein may bemanufactured, used and licensed by or for the Government forgovernmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION For certain battlefield applications, it isdesirable to have a large number of packaged explosives, either mines ornoisemaking devices or both, dispersed in preselected areas of thebattlefield. An extremely advantageous method of accomplishing this isby aircraft deployment. This air dispersal necessitates the use of alarge outer container, in which the smaller packages are disposed, priorto dispersal. Normally, after the small explosive packages are prepared,they are placed in the container at the point of preparation. Theexplosives or noisemakes are generally packed in small, vapor permeable,packages such as fabric bags or plastic film packets.

In the past, the practice has been to render these explosives safe byimmersion in an environment of liquid halocarbon. The immersedexplosives were then pack aged and shipped. These attempts to render theexplosives safe by treatment with such an environment have not beencompletely satisfactory.

In addition to safety considerations, it was necessary to develop asystem which would chemically desensitize the explosive for apre-determined amount of time and then allow the explosive to armitself. This, in essence, is a chemically-armed mine system. The largecontainer used to disperse the small packages had to be capable ofcontaining the explosives in both storage and battlefield conditions, ina desensitized, unarmed manner until they were deployed. This wasespecially difficult with a liquid halocarbon system because of thelikelihood of solvent evaporation and premature arming of the explosiveif the large container was pierced by rifle fire or shrapnel. Inaddition, if any leaks developed during shipping or storage throughaccident or rough handling, the explosive packages might arm prematurelyand cause serious damage.

Attempts have been made to solve this problem by incorporating gellingagents into the halocarbon system to prevent escape of thisdesensitizing liquid. While these attempts are practical, they areexpensive, and mines which are exposed to the gelling agent have atendency to leave trails of this material on foliage that has come incontact with them thereby eliminating the advantage of using this typeof mine in certain heavily foliated areas. Additionally, the possiblityexists of a gel forming on the mine package, thus preventing evaporationof the halocarbon and subsequent arming of the mine. Under storageconditions quite a bit of time can pass before a leak in one of thesecanisters is observed and ifthe leak is large enough, the gel may notplug the hole and consequently the explosvie will arm. Further, theseattempts have not added a positive method of completely desensitizingthe mines if for any reason the halocarbon fluid is prematurelyexhausted.

SUMMARY OF THE INENTION It is, therefore, an object of this invention toprovide a safety device which will insure a positive and permanentdesensitization of prematurely activated chemically-armed mines.

A further object is to provide a device which will insure the safety ofchemically-armed mines without introducing the possibility of prematureaccidental deactivation.

Another object is to provide a more tactically advantageous method ofdeploying che'mically-anned mines in foliated areas.

Yet another object is to provide an economical means of insuring safetyduring storage, shipping and deployment of chemically-armed mines.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same become better understood byreference to the drawings and the following description, wherein it isshown that the above-mentioned objects are attained and the prior artdeficiencies are overcome by the use of the device of my invention whichincludes a fluid which will permanently desensitize the explosivecomposition of the mine, encapsulated in a sealed frangible containerwhich is, in turn, partially enclosed ina material that swells throughcontact with certain organic liquids and then forcefully contracts whenthis contact is removed thereby crushing the container and releasing thedeactivating fluid, thus enabling this fluid to come in con tact withthe explosive composition of the mine.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a cross-sectional view ofthe item in which my invention may be used.

FIG. 2 is an enlarged cross-sectional view of the safety device shown inFIG. l in its intact, inactive state. I

FIG. 3 is an enlarged cross-sectional view of the safety device shown inFIG. 11 in its activated state.

Throughout the drawings the same numerals refer to the same items.

DESCRIPTION OF A PREFERRED EMBODIMENT My invention can best be shown inthe context of the entire munition. As shown in FIG. 1, the safetydevice 10 is placed in the mine dispenser l2 and thus immersed in thedesensitizing liquid 14. The mines 16, composed of a permeable plasticenvelope 18, filled with explosive 20 are then disposed in the dispenser12. The dispenser I2 is provided with an automatic ejection means 22 anda remotely controllable opening means 24 for use in deploying the mines16 from aircraft. The safey device 10 while immersed in thedesensitizing liquid M remains inactive. As shown in FIG. 2, the safetydevice It) is composed of a frangible container 24 which is filled witha sterilizing liquid or solution 26 and then sealed. The container 24 isthen partially enclosed in a pre-treated swollen casing 28. The casing28 is made of material specifically selected to swell under theinfluence of the desensitizing liquid 14.

The safety device 10 remains inactive so long as it is immersed in thedesensitizing liquid 14. As shown in FIG. 3, if for any reason thedesensitizing liquid 14 is exhausted, the casing 28 begins to contract,thus cracking the container 24 and permitting the sterilizing liquid 26to contact the mines l6, permeate the envelopes l8 and permanentlysterilize or deactivate the contained explosive 20. If the desensitizingliquid 14 is not exhausted before deployment, the safety device 10 issimply ejected with the mines 16 and will no longer be in a position tocause sterilization.

In operation, the encasing material selected is formed into a tube 28having an internal diameter of 80 to 90 percent of the outer diameter ofthe frangible container 24 around which it is to be placed. The tube iscut into smaller cylindrical sections and immersed for 24 hours in thedesensitizing liquid medium 14 in which it will be kept in its finaluse. The liquid 14 will usually be a halogenated aliphatic hydrocarbon.The encasing material is so selected and compounded that it expands byswelling action under the influence of the liquid 14 until the innerdiameter of tube 28 is slightly larger than the outer diameter of thecontainer 24 around which it is to be placed. The tube section is thenslipped over the container 24, where it may be held in place by anyconvenient means. The container 24 is and casing 28 are from that timeon maintained immersed in the desensitizing liquid 14. This sameselected liquid 14 acts as the desensitizing liquid for mine explosives,which are activated by the lead azide used in various fuzingarrangements. Normally, should an accidental leak occur, thedesensitizing liquid 14 would flow out of the container causing theexplosive 20 to dry out and become sensitized, creating a hazardouscondition. The presence of the safety device makes this eventuality muchless hazardous. As the liquid 14 begins to evaporate, the encasing tube28 around the container 24 shrinks in diameter as its dries, creatingstrong pressures around the container 24; this causes the container 24to break, spilling the contents 26 onto the mines 16, thus initiatingdestruction and deactivation of the explosive 20.

In lieu of the sealed frangible container, a different type of containermay be used, which has one or more openings capable of being closed by arubber stopper. The container may be filled with the sterilizing liquidor solution and tightly stoppered with stoppers which were manufacturedfrom the same selected rubber compound used for the encasing materialand which had been immersed for the necessary swelling time in theliquid to be used as the desensitizer. The container can be so placedinside the mine-containing canister that the sterilizing liquid willleak out should the stoppers be withdrawn. If the canister is now openedand the desensitizing liquid is withdrawn or permittedv to evaporate,then the rubber stoppers will shrink and permit the contents to leak outonto the explosive; thus desensitizing it.

The choice ofdesensitizing liquid is governed by criteria ofnon-reactivity with the explosive and an evaporation rate that willpermit practical arming or drying times for theitems. Any liquid whichwill meet these criteria can be used, for example 1,1,2 trichloro-,1,2,2 trifluoroethane; l,l,2,2 tetrachloro-, 1,2 'd'it'luoroethane;l,l,2,2 tetrafluoro- 1,2 dibromoethane; carbon tetrachloride andtetrachloroethylene. It has been found that halocarbons of a chainlength of one or two carbon atoms containing at least one halogensubstituent are preferred, such as perchloroethylene. These halocarbonspreferably have a boiling point between about 30 C to 120 C.

The sterilizing liquid must be capable of permanently deactivating theexplosive with which it comes in contact. Choice ofliquid or solutionwill ultimately depend on the type of explosive used. For example, anaqueous solution of a strong base, such as sodium or potassium hydroxideworks well with lead azide containing explosives as it destroys theazide. Additionally, the aqueous portion of the solution deactivates anysecondary explosives contained. The amount to be used depends, ofcourse, on the amount of explosive to be sterilized.

The explosive mixtures that may be permanently sterilized by thesterilizing liquid compose two major classes. First, impact sensitivepyrotechnic or noisemaking compositions. This class is usually made upof sensitive explosives, such as mixture of red phosphorous, potassiumchlorate or perchlorate and ground glass. Any combination of a mixtureof a strong oxidizer, abrasive agent and pyrotechnic fuel can be used toform the pressure sensitive mines. Second, explosive mixtures composedof secondary explosives, such as RDX, and primary explosives, such aslead styphnate or lead azide, may be used. The choice of secondaryexplosive is largely governed by reliability for example, PETN or HMX,may be used advantageously as well as any common secondary explosive.

The permeable envelope material used for the mine is selected for itsnonreactivity and its permeability towards both the desensitizing liquidand the sterilizing liquid. For example, cotton duck may be used as wellas certain films which are permeable to these liquids, such as Alathonor .Tyvek polyethylene film (both names are registered trademarks of E.l. DuPont de Nemours & Co.). The thickness of the film may be varied toachieve diverse permeation rates.

The encasing material is selected for its ability to swell under theinfluence of the desensitizing liquid used and to forcefully contract inthe absence of such fluid. The thickness of this material will partiallygovern the forcefulness of its contraction. l have found that materialsof choice for the encasing material are compounds such as isoprene,butadiene-styrene, isobutylene-isoprene and silicones. Many rubber-likecompounds or materials, as described in Army Material CommandPublication AMCP-706, formerly Ordnance Corps Pamphlet ORDP 20-3l0entitled Ordnance Materials Handbook Rubber and Rubber-like Materials,dated December, 1956, mayalso be selected, using the above-mentionedcriteria.

The frangible container may be fabricated from glass or plastic or anymaterial which is non reactive with both the desensitizing liquid-andthe sterilization liquid. Additionally, this material must be frangibleto be eas-' ily broken by the encasing material.

l have found by the use of my invention thata standard canister ordispenser can be completely sterilized within a few hours afterexhaustion of the desensitizing liquid. v

Summarizing, the safety device of my invention employs a frangiblecontainer filled with a fluid capable of permanently sterilizing ordeactivating a selected explosive. This frangible container is partiallyencased in a material which has the capability of swelling under theinfluence of selected liquids and contracting forcefully, afterswelling, in the absence of these liquids. My invention is particularlyuseful in the case of chemically-armed mines which are stored anddispensed in a reversibly desensitized state by the use of adesensitizing liquid which liquid also has the capacity to swell theaforementioned encasing material.

It should be understood, of course, that the foregoing disclosurerelates to only preferred embodiments of my invention and that numerousmodifications or alterations may be made therein without departing fromthe spirit and the scope of my invention.

1 claim:

1. The combination of a plurality of liquidpermeable,reversibly-desensitized, chemically-armed mines immersed in a liquiddesensitizing medium, with a safety device comprising:

able, reversibly desensitized, chemically-armed mines immersed in aliquid desensitizing medium, with a safety device comprising: 2

a sterilization liquid capable of permanently deactivating said mines;

frangible means, immersed in said liquid desensitizing medium, forcontaining said sterilization liquid in close proximity to said mines;

means for opening said containing means and releas ing saidsterilization liquid to permeate and deactivate said mines, said openingmeans comprising a member that expands in contact with said liquiddesensitizing medium and shrinks in the absence of said medium.

3. The combination as defined in claim 2 wherein said sterilizationliquid is an aqueous solution ofa sterilizing agent being, saidsterilizing agent capable of re acting with the explosive contained insaid mines and thereby deactivating said explosive.

4. The combination as defined in claim 3 wherein said sterilizing agentis an aqueous solution of a strong base.

5. The combination as defined in claim 4 wherein said sterilizing agentis an aqueous solution of a compound selected from the group consistingof sodium hydroxide and potassium hydroxide.

6. The combination as defined in claim 2 wherein said opening means is apolymeric material partially encasing said containing means, saidpolymeric material selected from the group consisting of siliconerubber, buna rubber and styrene rubber.

7. The combination of a plurality of liquid permeable, reversiblydesensitized, chemically-armed mines immersed in a liquid desensitizingmedium, with a safety device comprising:

a frangible sealed glass ampoule immersed in said liquid desensitizingmedium in close proximity to said mines;

a sterilization liquid capable of permanently deactivating said minescontained in said ampoule, said sterilization liquid being selected fromthe group consisting of a 10% by weight. aqueous solution of potassiumhydroxide and a 10 percent by weight aqueous solution of sodiumhydroxide;

means for breaking said ampoule and releasing said liquids, said meansresponding to the absence of said liquid medium with a contractile forcesufficient to break said ampoule, said means comprising a tubular casingmounted on and partially enveloping said ampoule, said casing beingfabricated from a polymeric material selected from the group consistingof isoprene, silicone, butadiene-styrene and isobutylene-styrene.

2. The combination of a plurality of liquid permeable, reversiblydesensitized, chemically-armed mines immersed in a liquid desensiTizingmedium, with a safety device comprising: a sterilization liquid capableof permanently deactivating said mines; frangible means, immersed insaid liquid desensitizing medium, for containing said sterilizationliquid in close proximity to said mines; means for opening saidcontaining means and releasing said sterilization liquid to permeate anddeactivate said mines, said opening means comprising a member thatexpands in contact with said liquid desensitizing medium and shrinks inthe absence of said medium.
 3. The combination as defined in claim 2wherein said sterilization liquid is an aqueous solution of asterilizing agent being, said sterilizing agent capable of reacting withthe explosive contained in said mines and thereby deactivating saidexplosive.
 4. The combination as defined in claim 3 wherein saidsterilizing agent is an aqueous solution of a strong base.
 5. Thecombination as defined in claim 4 wherein said sterilizing agent is anaqueous solution of a compound selected from the group consisting ofsodium hydroxide and potassium hydroxide.
 6. The combination as definedin claim 2 wherein said opening means is a polymeric material partiallyencasing said containing means, said polymeric material selected fromthe group consisting of silicone rubber, buna rubber and styrene rubber.7. The combination of a plurality of liquid permeable, reversiblydesensitized, chemically-armed mines immersed in a liquid desensitizingmedium, with a safety device comprising: a frangible sealed glassampoule immersed in said liquid desensitizing medium in close proximityto said mines; a sterilization liquid capable of permanentlydeactivating said mines contained in said ampoule, said sterilizationliquid being selected from the group consisting of a 10% by weightaqueous solution of potassium hydroxide and a 10 percent by weightaqueous solution of sodium hydroxide; means for breaking said ampouleand releasing said liquids, said means responding to the absence of saidliquid medium with a contractile force sufficient to break said ampoule,said means comprising a tubular casing mounted on and partiallyenveloping said ampoule, said casing being fabricated from a polymericmaterial selected from the group consisting of isoprene, silicone,butadiene-styrene and isobutylene-styrene.